Melanoma and non-melanoma skin cancers among commercial airline pilots have been reported to occur at increased rates. The reasons for these increases are unclear, but causes postulated in the literature include leisure sun exposure, ionizing radiation, and circadian disruption. Recent preliminary findings have suggested an age-adjusted statistically significant association between night flying (as a surrogate measure for circadian disruption) and both melanoma and nonmelanoma skin cancers. This association occurred in the absence of any indication that night fliers engaged in more frequent daytime leisure sun exposure. The purpose of this study is to use a case-control design to investigate the role of circadian disruption in the prevalence of skin cancer. The specific aim is to test the hypothesis that night flying is associated with increased prevalence of skin cancer among commercial airline pilots. Skin cancer rates will be adjusted for lifestyle (including leisure sun exposure), occupational exposures (including ionizing radiation), age and other established medical risk factors. Preliminary evidence suggests that those pilots experiencing the greatest circadian disruption will also have the highest skin cancer rates. A secondary analysis will examine melanoma and non-melanoma separately. Access to the pilot population will be achieved through collaboration with the Air Line Pilots Association International. Information will be collected using survey methodology. Because skin cancer is the most common type of cancer in the United States, etiological information gained from this study will benefit not only pilots and other night or rotating shift workers, but the general population, in controlling the incidence of this disease.